ruff/crates/ruff_python_ast/src/whitespace.rs

use ruff_text_size::{TextRange, TextSize};
use rustpython_parser::ast::Ranged;

use crate::source_code::Locator;

/// Extract the leading indentation from a line.
#[inline]
pub fn indentation<'a, T>(locator: &'a Locator, located: &T) -> Option<&'a str>
where
    T: Ranged,
{
    indentation_at_offset(locator, located.start())
}

/// Extract the leading indentation from a line.
pub fn indentation_at_offset<'a>(locator: &'a Locator, offset: TextSize) -> Option<&'a str> {
    let line_start = locator.line_start(offset);
    let indentation = &locator.contents()[TextRange::new(line_start, offset)];

    if indentation.chars().all(char::is_whitespace) {
        Some(indentation)
    } else {
        None
    }
}

/// Extract the leading words from a line of text.
pub fn leading_words(line: &str) -> &str {
    let line = line.trim();
    line.find(|char: char| !char.is_alphanumeric() && !char.is_whitespace())
        .map_or(line, |index| &line[..index])
}

/// Extract the leading whitespace from a line of text.
pub fn leading_space(line: &str) -> &str {
    line.find(|char: char| !char.is_whitespace())
        .map_or(line, |index| &line[..index])
}

/// Replace any non-whitespace characters from an indentation string.
pub fn clean(indentation: &str) -> String {
    indentation
        .chars()
        .map(|char| if char.is_whitespace() { char } else { ' ' })
        .collect()
}

/// Returns `true` for [whitespace](https://docs.python.org/3/reference/lexical_analysis.html#whitespace-between-tokens)
/// or new-line characters.
pub const fn is_python_whitespace(c: char) -> bool {
    matches!(
        c,
        ' ' | '\n' | '\t' | '\r' |
        // Form-feed
        '\x0C'
    )
}